The effects "destroy a Field Spell Card" and "gain 1000 Life Points" of "Ancient Fairy Dragon" are considered to resolve simultaneously. However, if you choose to resolve the "add 1 Field Spell Card to your hand" effect, then that occurs afterwards.

Previously Official Rulings

These TCG rulings were issued by Upper Deck Entertainment and have since been deemed unofficial by Konami.[7] They were previously considered official and can still be correct, as long as they follow the official gameplay rules, or unless Konami has issued a ruling that says otherwise. References: [8][9][10][11][12][13][14][15][16]